Conventionally, for wiring structures of transportation devices such as motor vehicle and airplane and of industrial devices such as robot, a structure in the form called wire harness including a plurality of bound electric wires with terminals has been used. Conventionally, the material to constitute a conductor for an electric wire of the wire harness is mostly copper having an excellent electrical conductivity or a copper-based material such as copper alloy.
With the recent rapid enhancement in performance and capabilities of the motor vehicle and with the increase of a variety of electrical devices, control devices and the like that are mounted on the vehicle, electric wires used for these devices also tend to increase. Meanwhile, recently for the sake of environmental conservation, improved fuel economy of motor vehicles and airplanes for example has been desired. A reduced weight can improve the fuel economy. In view of this, for the purpose of reduction in weight of electric wires, studies are conducted on use, as a conductor, of aluminum having its specific gravity which is about one-third that of copper. For instance, there has been an example where pure aluminum is used for a conductor for an electric wire of 10 mm2 or more such as a battery cable of a motor vehicle. Pure aluminum, however, has a lower strength and a lower fatigue resistance than a copper-based material, and therefore, pure aluminum is difficult to be applied to common conductors for electric wires such as those having a conductor's cross-sectional area of 1.5 mm2 or less. In contrast, Patent Document 1 discloses an electric wire for a wire harness of a motor vehicle that is made of an aluminum alloy having a higher strength than pure aluminum.